Question

Discuss the theories concerning the origin of life and evolution of man.

Answer 1

Origin of life and Evolution of Man

The evolution of modern humans from the hominid ancestor is commonly considered to involve 4 major steps: evolving terrestrially, bipedalism, a large brain and civilization.

Inquisitive thinkers of the ancient time speculated about the origin of life as well as appearance of man on earth. One such speculation, which is as old as human thought, is commonly known as the theory of spontaneous generation of life. It was believed that life originated spontaneously from organic components of the environment that existed since the formation of our planet. A series of physicochemical processes took place and in course of time that produced living organisms from inert non-living matters.
In the present time also it is believed that life began spontaneously by chance because of mixing of different elements in varied proportions. The scientists do not know yet how this happened. They are still carrying on different types of experiments. When living organisms were being formed, the environmental condition on the earth was not the same as it is today. The atmospheric components of that time reacted with natural electric discharge, solar energy, volcanic heat and the like, as a result of which different carbon compounds were produced. These compounds are considered to be the basis for the formation of life.

Some thinkers believed in extra-terrestrial origin of life. Their idea was that the earth received ultra-microscopic germs of life from other planets and those were the basic seeds to produce life. On the other hand, to some others life had no beginning. Life has always existed in our planet.

For our convenience following R.S. Lull we can discuss the theories concerning origin of life and evolution of man under four broad categories, which are as follows: (a) theory or eternity: (b) theory of special creation (creationism); (c) theory of cataclysm or catastrophism and (d) theory of organic evolution.

Theory of Eternity:

According to this theory universe is unchangeable. The organism were there from the very beginning and these will always be there in their original forms. Only a very few men of science gave importance to this view.
Theory of Special Creation:

According to this theory all kinds of life were created by a supernatural power, which can be referred to as God, and that these forms of life have not been changed from the time of their creation. The followers of this theory believed that all creations of God are arranged in a scale of Nature or the chain of Being.

According to the theory of special creation the world was created in six days. The earth was created on the first day. Animal and plant kingdoms were created on the third day. All the creatures that exist in the earth were created by the fifth and sixth days. Father Saurez (1548-1617) -strongly advocated this theory.

Theory of Cataclysm or Catastrophism:

Georges Cuvier (1769-1832), a French scientist proposed this theory. His observation was based on the fossil remains of varied organisms. He believed that the nature of forms of life was never the same, it was changed time to time. The earth experienced natural calamities several times and that destroyed the animal species. One was replaced by another increasingly higher form in terms of complexity of structure every time, when the earth settled after a great catastrophe. He did not believe in continuous evolution. To him contemporary species did not develop by modifications of these found in fossilized forms. According to him, in the first stage there were corels, molluscs and crustaceans. Then emerged the first plants, followed by the fish and reptiles. After that birds and mammals emerged. Finally, man appeared after the last geological revolution and that happened about five or six thousand years ago.)

Theory of Organic Evolution:

In the works of the ancient Roman and Greek philosophers and thinkers indications of their ideas of a certain continuity of living organisms and even of evolution are fond. For example, Thales of Miletus (636-546 B.CJ believed that de originated in water and hence water may be regarded as the mother of life. He thought that man had evolved from fish, which came out of water and then developed to its present form in land. According to Pythagoras (570-496 B.CJ "nothing in the vast universe perishes, rather everything varies and changes shape".
It may be mentioned that in the ancient Hindu religious thoughts also one gets indication of conception of evolution. The best example of it is the ten incarnations (Dash-avatar) of Lord Krishna. The first one is fish (Matsya) and it was believed by the western thinkers also that life originated in water. The next one was Kurma, an amphibian, Varaha represents the land-living animals. Nrisimha tells of a stage of half-man and half-animal. Even now a school of scientists believe that early man was short statured. Vamana, an incarnation of Lord Krishna, represents that type of early man. Ten incarnations tell us about cultural evolution as well. Parasurama had his axe, which is technically inferior to bow and arrow of Rama and therefore. Ram could defeat Parasuram. This perhaps, could be compared with the food gathering stage. Then came the food producing stage by domestication of animal (Lord Krishna in his childhood looked after cattle) and agriculture (Plough in the hand of Balarama).

Evolution:

Evolution is defined as the change in the heritable characteristics of biological populations over successive generations and relies on the process of natural selection.